Detachably affixed counterweight and method of assembly

Abstract

A compressor or pump assembly including a housing, a compression mechanism disposed within the housing, a shaft operatively connecting the compression mechanism and a drive source, the shaft having an axis of rotation and first and second surfaces, the shaft axis of rotation disposed between the first and second shaft surfaces, and a counterweight disposed about the shaft and comprising first and second portions, the first counterweight portion generally U-shaped, having first and second arms, the first arm in contact with the first shaft surface, the second arm in contact with the second shaft surface, the second counterweight portion extending between the first and second arms and attached to the first counterweight portion, the shaft captured between the first and second counterweight portions, whereby rotation is imparted to the counterweight through the interface of the shaft surfaces and the arms.

What is claimed is: 
     
       1. A compressor or pump assembly comprising: a housing;   a compression mechanism disposed within said housing;   a shaft operatively connecting said compression mechanism and a drive source, said shaft having an axis of rotation and first and second surfaces, said shaft axis of rotation disposed between said first and second shaft surfaces; and   a counterweight disposed about said shaft and comprising first and second portions, said first and second counterweight portions each being substantially rigid, said first counterweight portion generally U-shaped, having first and second arms, said first arm in contact with said first shaft surface, said second arm in contact with said second shaft surface, said second counterweight portion extending between said first and second arms and attached to said first counterweight portion, said shaft captured between said first and second counterweight portions;   whereby rotation is imparted to said counterweight through said the interface of said shaft surfaces and said arms.   
     
     
       2. The compressor or pump assembly of claim 1, wherein said shaft is provided with at least one shoulder adjacent at least one of said first and second shaft surfaces, whereby said counterweight is restricted from movement in the direction of said axis of rotation. 
     
     
       3. The compressor or pump assembly of claim 2, wherein said at least one shaft shoulder lies substantially in a plane normal to said axis of rotation. 
     
     
       4. The compressor or pump assembly of claim 1, wherein said first and second shaft surfaces are substantially flat. 
     
     
       5. The compressor or pump assembly of claim 4, wherein said first and second shaft surfaces lie in substantially parallel planes. 
     
     
       6. The compressor or pump assembly of claim 1, wherein said drive source is an electric motor. 
     
     
       7. The compressor or pump assembly of claim 6, wherein said motor is disposed in said housing. 
     
     
       8. The compressor or pump assembly of claim 1, wherein said shaft is provided with an eccentric portion adjacent said counterweight. 
     
     
       9. The compressor or pump assembly of claim 8, wherein said shaft is radially supported by a pair of bearings, said eccentric portion and said counterweight disposed between said bearings. 
     
     
       10. The compressor or pump assembly of claim 9, wherein said counterweight is a first counterweight, and further comprising a second counterweight rotatably fixed to said shaft, said eccentric portion disposed between said first and second counterweights, said first and second counterweights disposed between said bearings. 
     
     
       11. The compressor or pump assembly of claim 1, wherein said first and second arms are provided with respective first and second surfaces which respectively slidably contact said first and second shaft surfaces. 
     
     
       12. The compressor or pump assembly of claim 11, wherein said first and second shaft surfaces and said first and second arm surfaces are substantially flat. 
     
     
       13. The compressor or pump assembly of claim 12, wherein said first and second shaft surfaces and said first and second arm surfaces substantially lie in substantially parallel planes. 
     
     
       14. The compressor or pump assembly of claim 1, wherein said axis of rotation is substantially normal to a first plane, said first and second counterweight portions having interfacing axial surfaces which are substantially parallel with said first plane. 
     
     
       15. The compressor or pump assembly of claim 14, wherein said interfacing axial surface of said first counterweight portion comprises surfaces of said first and second arms. 
     
     
       16. The compressor or pump assembly of claim 15, wherein said first and second counterweight portions each have at least two angled surfaces, each of said four angled surfaces being nonparallel with said first plane, said first and second counterweight portions being in contact through two abutting pairs of said angled surfaces, one said angled surface of each said abutting pair of said angled surfaces being provided on each said arm of said first counterweight portion, the other said angled surface of each said abutting pair of said angled surfaces being provided on said second counterweight portion, each said angled surface of said first counterweight portion having an inner edge and an outer edge, each said outer edge radially farther from said axis of rotation than its adjacent inner edge, said inner edges of said first counterweight portion separated by a first distance, said inner edges of said second counterweight portion separated by a second distance, said first distance greater than said second distance, whereby said arms are urged into increasing compressive contact with said shaft surfaces as said interfacing axial surfaces are brought into closer proximity to one another. 
     
     
       17. The compressor or pump assembly of claim 16, wherein one pair of said abutting angled surfaces interface substantially along a second plane, and the other pair of said abutting angled surfaces interface substantially along a third plane, said second and third planes each having an acute angle with said first plane and intersect along a line which lies radially between said first and second shaft surfaces, whereby said arms are urged into increasing compressive contact with said shaft surfaces as said interfacing axial surfaces are brought into closer proximity to one another. 
     
     
       18. The compressor or pump assembly of claim 17, wherein each said acute angle is at least about 30°. 
     
     
       19. The compressor or pump assembly of claim 15, further comprising means for clamping said shaft between said arms as said axial interfacing surfaces are brought into closer engagement with each other. 
     
     
       20. The compressor or pump assembly of claim 1, wherein said first and second counterweight portions are threadedly attached to one another. 
     
     
       21. A method of attaching a counterweight to a pump or compressor crankshaft, comprising the steps of: providing a crankshaft with first and second surfaces, and a counterweight having first, substantially U-shaped portion with first and second arms and a second portion;   straddling the crankshaft with the first counterweight portion, sliding the arms of the first counterweight portion over the crankshaft surfaces;   overlying axially interfacing surfaces of the first and second counterweight portions, whereby the counterweight surrounds the crankshaft; and   attaching the first and second counterweight portions to one another.   
     
     
       22. The method of claim 21, further comprising the steps of: bringing the first and second counterweight portions into increasingly tighter engagement with one another;   clamping the first and second arms against their adjacent crankshaft surfaces.   
     
     
       23. The method of claim 21, wherein said attaching step comprises the steps of: inserting a screw into a hole provided in one of the first and second counterweight portions; and   engaging the threads of a screw with mating threads provided in the other of the first and second counterweight portions.